From patchwork Fri Aug 12 07:15:26 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?b?SmFuIETEhWJyb8Wb?= X-Patchwork-Id: 597138 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 647EDC00140 for ; Fri, 12 Aug 2022 07:16:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237243AbiHLHQE (ORCPT ); Fri, 12 Aug 2022 03:16:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235031AbiHLHQB (ORCPT ); Fri, 12 Aug 2022 03:16:01 -0400 Received: from mail-lf1-x132.google.com (mail-lf1-x132.google.com [IPv6:2a00:1450:4864:20::132]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D9E2E1D314 for ; Fri, 12 Aug 2022 00:15:59 -0700 (PDT) Received: by mail-lf1-x132.google.com with SMTP id u3so190088lfk.8 for ; Fri, 12 Aug 2022 00:15:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=semihalf.com; s=google; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc; bh=Ibyyw8eyBkdWgpPHklA51urSo/P4KWDrlMWV8p61Auo=; b=np5q3pIwqTobXVFF0oUoVSqBBS1dsAB6312LzrhJiWQA9FoHNz8K76CUd4a0Rl/Wvs +0MDO8gWZxLCZgdw61LT2+rmYqi+JiAbiFVU8LYPQwJ4Yu795ARPgu40X7ccwJoO+dL6 MvqgsZp7Ro6zDS+QCw/UgRUm9fkk9JPXt5TOzWnpqehMVNdVlBxXbGbqJRgETM19ehBT zXFEUBtthU6Wps/TX14JYkHlmzSvlPEg/ooq174WvMgPMQNz01ZsfIRa/zoXfriFkl5z SASolv5yVtvrlFwJyYL7ydHJ/naRfImKr3nUr8E3k7Z5VIt1DZyY/dXjACfnRiOej1/l h6/g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc; bh=Ibyyw8eyBkdWgpPHklA51urSo/P4KWDrlMWV8p61Auo=; b=pBAn4ZeSKbe8fOgTv2m2V85hBnO5Hj2DQ2Gj48qLew1DoyZ+eC1e12QSnacnE3SabB G5pmEl/SYM0pLxe5VdqLpx0eE+vgX1vt2QEXBO4SDntl/F5sSSdpe2cixA7HDz4sXGba 8wl547FTo1qj0ofgqaOqKJYL6o1hc+a/Ax8MLBrmiSymDuKB/p9sVCANd1gApcXNfjxd WWBFZ7dKis/kvqL63S/+3/9+ypeBJVjtk83kmgENp2aZPZrJX3T/mAPctM3yGq2VhcPw LtnKXDKH9UtghUW0oezUsvHaYn3xHWgzwNA47VeGC9Ssdq3tepNL3v7/N6WQmWFGncy0 LBYg== X-Gm-Message-State: ACgBeo0DCpRQsAfGIYF5QN2xS7/DDKHAppTQgl9hJxsrHBWqZGjCTE9a gkKx+zgQkNmGISeafvnJVBZV5A== X-Google-Smtp-Source: AA6agR4+8bVn1EQrVmPpWj2TrlLC5ReowaoSXciZ23clKO04B7aRWS0X2mRe6WqLtDv0Ie2pA4VTPQ== X-Received: by 2002:ac2:59c2:0:b0:48b:1827:dd43 with SMTP id x2-20020ac259c2000000b0048b1827dd43mr930481lfn.132.1660288558149; Fri, 12 Aug 2022 00:15:58 -0700 (PDT) Received: from dabros-l.room.semihalf.net ([185.157.14.92]) by smtp.gmail.com with ESMTPSA id u21-20020a05651206d500b0048b0a5293ccsm115624lff.78.2022.08.12.00.15.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Aug 2022 00:15:57 -0700 (PDT) From: Jan Dabros To: linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, jarkko.nikula@linux.intel.com, andriy.shevchenko@linux.intel.com Cc: mika.westerberg@linux.intel.com, rrangel@chromium.org, mw@semihalf.com, upstream@semihalf.com, jsd@semihalf.com Subject: [PATCH v2] i2c: designware: Introduce semaphore reservation timer to AMDPSP driver Date: Fri, 12 Aug 2022 09:15:26 +0200 Message-Id: <20220812071526.414285-1-jsd@semihalf.com> X-Mailer: git-send-email 2.37.1.595.g718a3a8f04-goog MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org In order to optimize performance, limit amount of back and forth transactions between x86 and PSP. This is done by introduction of semaphore reservation period - that is window in which x86 isn't releasing the bus immediately after each I2C transaction. In order to protect PSP from being starved while waiting for arbitration, after a programmed time bus is automatically released by a deferred function. Signed-off-by: Jan Dabros Acked-by: Jarkko Nikula --- drivers/i2c/busses/i2c-designware-amdpsp.c | 68 +++++++++++++++++----- 1 file changed, 53 insertions(+), 15 deletions(-) diff --git a/drivers/i2c/busses/i2c-designware-amdpsp.c b/drivers/i2c/busses/i2c-designware-amdpsp.c index b624356c945f..b9bdc7db89df 100644 --- a/drivers/i2c/busses/i2c-designware-amdpsp.c +++ b/drivers/i2c/busses/i2c-designware-amdpsp.c @@ -6,6 +6,7 @@ #include #include #include +#include #include @@ -15,6 +16,8 @@ #define PSP_MBOX_OFFSET 0x10570 #define PSP_CMD_TIMEOUT_US (500 * USEC_PER_MSEC) +#define PSP_I2C_RESERVATION_TIME_MS 100 + #define PSP_I2C_REQ_BUS_CMD 0x64 #define PSP_I2C_REQ_RETRY_CNT 400 #define PSP_I2C_REQ_RETRY_DELAY_US (25 * USEC_PER_MSEC) @@ -240,6 +243,42 @@ static int psp_send_i2c_req(enum psp_i2c_req_type i2c_req_type) return ret; } +static void release_bus(void) +{ + int status; + + if (!psp_i2c_sem_acquired) + return; + + status = psp_send_i2c_req(PSP_I2C_REQ_RELEASE); + if (status) + return; + + dev_dbg(psp_i2c_dev, "PSP semaphore held for %ums\n", + jiffies_to_msecs(jiffies - psp_i2c_sem_acquired)); + + psp_i2c_sem_acquired = 0; +} + +static void psp_release_i2c_bus_deferred(struct work_struct *work) +{ + + mutex_lock(&psp_i2c_access_mutex); + + /* + * If there is any pending transaction, cannot release the bus here. + * psp_release_i2c_bus will take care of this later. + */ + if (psp_i2c_access_count) + goto cleanup; + + release_bus(); + +cleanup: + mutex_unlock(&psp_i2c_access_mutex); +} +static DECLARE_DELAYED_WORK(release_queue, psp_release_i2c_bus_deferred); + static int psp_acquire_i2c_bus(void) { int status; @@ -250,21 +289,23 @@ static int psp_acquire_i2c_bus(void) if (psp_i2c_mbox_fail) goto cleanup; + psp_i2c_access_count++; + /* - * Simply increment usage counter and return if PSP semaphore was - * already taken by kernel. + * No need to request bus arbitration once we are inside semaphore + * reservation period. */ - if (psp_i2c_access_count) { - psp_i2c_access_count++; + if (psp_i2c_sem_acquired) goto cleanup; - } status = psp_send_i2c_req(PSP_I2C_REQ_ACQUIRE); if (status) goto cleanup; psp_i2c_sem_acquired = jiffies; - psp_i2c_access_count++; + + schedule_delayed_work(&release_queue, + msecs_to_jiffies(PSP_I2C_RESERVATION_TIME_MS)); /* * In case of errors with PSP arbitrator psp_i2c_mbox_fail variable is @@ -279,8 +320,6 @@ static int psp_acquire_i2c_bus(void) static void psp_release_i2c_bus(void) { - int status; - mutex_lock(&psp_i2c_access_mutex); /* Return early if mailbox was malfunctional */ @@ -295,13 +334,12 @@ static void psp_release_i2c_bus(void) if (psp_i2c_access_count) goto cleanup; - /* Send a release command to PSP */ - status = psp_send_i2c_req(PSP_I2C_REQ_RELEASE); - if (status) - goto cleanup; - - dev_dbg(psp_i2c_dev, "PSP semaphore held for %ums\n", - jiffies_to_msecs(jiffies - psp_i2c_sem_acquired)); + /* + * Send a release command to PSP if the semaphore reservation timeout + * elapsed but x86 still owns the controller. + */ + if (!delayed_work_pending(&release_queue)) + release_bus(); cleanup: mutex_unlock(&psp_i2c_access_mutex);